Determining Speed Limits

Construction & Speed Surveys

When a new roadway is constructed or an existing roadway undergoes a significant change in surrounding land use or roadway characteristics, the City is required to perform a speed survey in accordance with the California Vehicle Code (CVC) and California Manual of Traffic Control Devices (MUTCD). A speed survey consists of measuring speeds with automated equipment in each direction of traffic on any given roadway segment. These measurements must be taken when traffic is flowing freely in fair weather with no unusual conditions present.

Speed Limits

The speed limit for any segment of road is set at the nearest 5 miles per hour (mph) increment of the 85th percentile speed of the speed survey. The 85th percentile speed is that speed at which 85% of the vehicles are traveling. 

For example, an 85th percentile speed of 41.5 on a speed survey would establish a speed limit of 40 mph, whereas an 85th percentile speed of 43.8 on a speed survey would establish a speed limit of 45 mph. An additional reduction of 5 mph may be taken if the Traffic Engineer feels it is warranted to meet the traffic safety needs of the community.

Enforcing Speed Limits

After the speed limit is adopted by the City Council and appropriate signs installed, the Police Department can legally enforce the posted speed limits. If no physical changes occur on the roadway, the speed survey is considered valid for a period of 7 years, and can be extended up to 10 years if conditions remain constant.

Traffic Resources